| Large complex eyes; 4, 5 or 6 antennae. (Family Alciopidae) | ||
| Small eyes; without antennae. (Family Iospilidae) | ||
| Poorly developed eyes; 4 antennea. Tentacular cirri present; uniramous parapodia. (Family Lopadorhynchidae) | ||
| Very small eyes; 4 antennae. 4 tentacular cirri; elongated pedal lobes on parapodia. (Family Pontodoridae) | ||
| Simple eyes and one pair of antennae; 2nd segment with long cirriform appendages. (Family Tomopteridae) | ||
| Without eyes or antennae. Nuchal organs present. Pygidium with a pair of flattened anal cirri. (Family Typhloscolecidae) | ||
| Without eyes or antennae; 4 long tentacular cirri. No nuchal organs or flattened anal cirri. Family Yndolaciidae) | ||
| Nine segments. Body and parapodia encased in transparent gelatinous sheath. (Family Flotidae) | ||
Too many to display...